As for the generating of drug-resistance microorganism by traditional antibiotics, many research focused on new therapeutic reagent, including many antibiotic peptides generated from animals. Antimicrobial peptides play important roles in the host innate defense mechanism by interacting and permeabilizing microbial membranes. The antibacterial peptides possibly exist in some plants, insects, Amphibia and mammals. The antibiotic of antibacterial peptides can fight against bacteria, fungus and even some virus. This kind of antibacterial peptide binds with lipid (more than 95%) and breaks the integrity of the membrance by departing of the lipid bilayer rapidly. On the other hand, it can add a small and short transportation on parallel lipid bilayer of the bacteria, so as to depolarize the cell membrance and break the original voltage gradient.
This kind of antibacterial peptide performs defensive protection function in host, which has been proved in fruit fly. When the fruit fly was infected by microbes and the expression of antibacterial peptide decrease, the survival rate of the fruit fly will decrease significantly. However, in mammals, it has been proved that this kind of antibacterial peptide performs defective protection function in defective bacterial killing of patients and mice with Cystic fibrosis. The antibacterial peptides which were found in mammals can be classified as cysteine-rich defensins and a variety of cathelicidin.
Cathelicidin contains a highly preserved signal sequence and a pre-area cathelin and the variation antibacterial sequence on C-terminal area. Many cathelicidin have unique cutting site on elastin protein kinase between negative charged cathelin area and positive charged c-terminal area. The protein hydrolysis reaction of the cutting site is observed and is necessary as antibacterial activity in neutrophil in cattle and pig. According to the contents and structures of the amino acids, the cathelicidin family can be classified into three groups: first group is having hydrophilic helix structure, such as LL-37, CRAMP, SMAP-29, PMAP-37, BMAP-27 and BMAP-28; and the second group is Arginine/Proline or Tryptophan-rich peptide, such as Bac5, Bac7, PR-39 and indolicidin; The third group is Cysteine-rich peptide, such as protegrins.
In academy, the non-antibiotic microbe therapy, such as the type of antibacterial peptide, could be the main axis of development in antibacterial drug in the future. Especially, the drug-resistance is becoming severer, it is utility for industry as a therapy for fishing farming and animal farming. It is hopeful to solve the secret worry coming from the overflow of antibiotic today.